Are the lower planes of double seismic zones caused by serpentine dehydration in subducting oceanic mantle?

Abstract

Research Article| April 01, 2001 Are the lower planes of double seismic zones caused by serpentine dehydration in subducting oceanic mantle? Simon M. Peacock Simon M. Peacock 1Department of Geological Sciences, Box 871404, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Geology (2001) 29 (4): 299–302. https://doi.org/10.1130/0091-7613(2001)029<0299:ATLPOD>2.0.CO;2 Article history received: 07 Jul 2000 rev-recd: 07 Dec 2000 accepted: 15 Dec 2000 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Simon M. Peacock; Are the lower planes of double seismic zones caused by serpentine dehydration in subducting oceanic mantle?. Geology 2001;; 29 (4): 299–302. doi: https://doi.org/10.1130/0091-7613(2001)029<0299:ATLPOD>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract In a number of subduction zones, earthquakes at 50–200 km depth define two dipping planes, separated by 20–40 km, that appear to merge downdip. Upper plane earthquakes are inferred to occur within the subducting oceanic crust, whereas lower plane earthquakes occur in the subducting oceanic mantle. Beneath northeast Japan, the results of a new finite-element heat-transfer model suggest that the lower seismic plane cuts across isotherms at a shallow angle. Lower plane earthquakes occur at ∼550–800 °C at 100 km depth and at ∼350–600 °C at 160 km depth. These conditions coincide with the dehydration reaction antigorite (serpentine) → forsterite + enstatite + H2O, which suggests that lower plane earthquakes may be triggered by dehydration embrittlement, which in turn suggests that the subducting oceanic mantle is partially hydrated. Serpentinization may occur in the trench–outer rise region, where faulting may promote infiltration of seawater several tens of kilometers into the oceanic lithosphere. If this hypothesis is correct, current subduction-zone H2O budgets may significantly underestimate the amount of bound H2O entering the "subduction factory." You do not have access to this content, please speak to your institutional administrator if you feel you should have access.